GM did not insulate them and they gave no trouble in literally millions of vehicles. Since they are out in the open however, it probably is not a bad idea to heat shrink them. It would give a more completed look.
I always remove those red and blue crimp covers by giving them a gentle twist. I then crimp, solder , and follow with shrink wrap. I follow up with dielectric grease on the terminals to prevent premature corrosion.